This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Dysregulation of the serotonergic system and abnormalities of the hypothalamic-pituitary-adrenal (HPA) axis have been suggested to play a role in the pathophysiology of major depression. Often stress is seen as a common precipitant of depression in vulnerable individuals. Excessive stimulation of the HPA axis following chronic stress results in the hypersecretion of cortisol, a common condition seen in many depressed patients. Normalization of circulating cortisol levels in depressed patients has been found to correlate with successful clinical treatment. Stress and adverse life events have been implicated in the etiology of depression and women are three times more likely than men to develop depression in relation to stressful life events, supporting the fact that women are twice as likely to suffer an episode of depression compared to men. The serotonin (5-HT) system appears to play a major role in the etiology of major depression and the response to antidepressant treatment. Classical as well as more recent antidepressant drugs appear to modulate 5-HT neurotransmission. The central hypothesis of this application is that stress-induced changes in serotonin-related transcription factors (NUDR, Freud-1 and Pet-1) play a significant role in regulating several serotonin-specific genes that control serotonin biosynthesis and neurotransmission following stress exposure. This hypothesis will be evaluated through the following specific aims: Aim 1. Determine specific alterations in the biosynthesis of the serotonin-related transcription factors in the dorsal raphe and prefrontal cortex of male rats exposed to chronic restraint stress. Aim 2. Determine specific alterations in the biosynthesis of serotonin-related transcription factors in the dorsal raphe and prefrontal cortex of female rats exposed to restraint stress. Aim 3. Study the effects of antidepressant treatment on the expression of Pet-1, Freud-1 and NUDR in male and female rats exposed to chronic restraint stress. Our long-term objectives are to elucidate how stress and gender differences modulate the expression of serotonin specific transcription factors and how these in turn regulate genes for the 5-HT1-A receptor, tryptophan hydroxylase 2 (TPH2) and the 5-HT transporter (5-HTT) as a necessary prerequisite to the development of novel therapeutics. The studies will utilize several biochemical and molecular biological procedures including in situ hybridization, Western blotting, real time PCR and cDNA synthesis to quantify protein and gene expression of the various serotonergic molecules and transcription factors in rat brain tissues from the midbrain dorsal raphe nucleus and prefrontal cortex. This proposal will be the first study to examine the expression of these novel serotonin-related transcription factors in an animal model of stress related to depression. Overall, the proposed research will elucidate the molecular mechanisms involved in the stress induced regulation of serotonin-related transcription factors and serotonin neurotransmission and may lead to the discovery of novel targets for the treatment of stress related depression and psychiatric illness.